What happens if you perform work in the main (UI) thread for a long time?

The main (UI) thread will be blocked, leading to the following consequences:

• The application will become unresponsive to user actions (button presses, scrolling, etc.).
• Animations and UI updates will stop.
• The system may display a "Application Not Responding" (ANR) dialog and suggest the user close the app.

All of these negatively impact the user experience and the stability of the application. For long-running operations (network requests, database work, complex calculations), background threads or asynchronous mechanisms should be used.